This invention relates to a method of attaching or installing, in the construction of a wall or floor, an upper or outer thin veneer facing of frangible cemetitious material such as, for example, terrazzo topping, onto a sub-surface of concrete.
A common method of making a terrazzo floor comprises applying a mortar underbed about two inches thick reinforced with wire mesh to a structural concrete slab and topping the mortar underbed with a layer of terrazzo of about one-half inch thickness for a resulting two and one-half to three inch floor thickness. However, the resulting concrete structural slab sub-surface tends to crack or move due to the presence of moisture, due to expansion and contraction from temperature changes, and to other causes which may include stresses, rupture or settling. In that the terrazzo topping is intimately bonded to the sub-surface by the mortar underbed, both of which are brittle and frangible, cracking or movement of the concrete sub-surface normally causes corresponding cracking and destruction of the terrazzo topping.
The thick combination of mortar underbed and terrazzo topping exerts a considerable total weight load on the supporting floor joists and, in multistory commercial and industrial buildings, necessitates the use of oversize construction members to carry the cumulative weight load from many floors. In addition, the thick terrazzo floor often presents problems in achieving a uniform floor height from room to room on the same level if certain floors are, for example, covered with broadloom or wood veneers.
Thin terrazzo floors have been constructed directly on the concrete slab sub-surface in attempts to overcome the aforementioned problems. However, the terrazzo veneer often will separate from the underlying slab sub-surface and "resonate", i.e. will vibrate, from pedestrian traffic thereon with resulting cracking and deterioration. Also, the frangible thin terrazzo veneer, without a mortar underbed, is particularly sensitive and prone to cracking due to movement of the concrete slab sub-surface.
This invention precludes the need for the mortar underbed normally required and provides a novel composite structure which substantially obviates cracking in the fragible upper or outer thin veneer facing due to fracture, cracking or other movement of the underlying sub-surface, reduces floor thickness and minimizes floor weight, while permitting the application of a facing veneer, such as a thin layer of terrazzo, as a wet slurry mix.